十八試空六号無線電信機二型 (18-shiki Ku-6 Gō musen denshinki 2-gata, Protoype 18 Ku 6 Wireless telegraph Model 2). The FD-1 (also known as H-5) was an experimental long range omnidirectional search radar for small patrol planes. Experiments were stopped due to inadequate range during flying tests. After the IJN decided to develop specialized AI radars for night fighters, development continued as a locator radar with the FD-2 radar with 4 forward facing Yagi antenna in stead of two.

Technical Specifications

十八試空六号無線電信機二型 / Prototype 18 Ku 6 Wireless Telegraph Model 2
Designation FD-1 or H-5
Object Patrol and Search
Research started June or December 1943
Finished February 1944
Operational status Not yet used
Installation Unknown
Frequency 0.6 meter / 500 kHz
Power Output (Peak) 2.5 kw
Pulse Length 3 µs
Repetition Frequency 1000 cycles per second
Weight  
Units build  
Transmitter Oscillation Circuit   Modulated Oscillator  
  Oscillator Valve T-321 x1
Receiver Intermed. Freq. 10 mc
Detector 1st 2400 2nd FM-2A05A
Local ocillator UN-955
Scope
Representation
Diameter 75 mm
Scanning Axis Sinusoidal
Scale None
Antenna Type 2x Yagi
one sending, one receiving
 
Gain 8db  
Beam Angle Horiz. θƒ = ~30°  
Vertical θƒ = ~30°  
Max. Range (Max.Effective Scale) 75 km theoretical
20 against merchant schips
Minimum Distance 600 m
Accuracy of Range ≃± 5%
Distance Discrimination ≃500 m
Accuracy of Bearing ± 0.5°
Angle Discrimination ≃ 60°
Operator Observer

Reports of the U.S. Naval Technical Mission to Japan

Excerpt of “Reports of the U.S. Naval Technical Mission to Japan, 1945-1946. Series E-02 Japanese Airborne Radar” page 20, detailing the electric schematic of the FD-1 Radar
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